I know how to do this in windows, but in Linux, it's not letting me move the brushes to the brushes folder in GIMP... It says "Error, Permission Denied." Actually, it says this to anything I want to move into a fold that is under "share." Help please? (I've been using Linux since LM8, but I'm still a noob )

Same as windows, there are 2 locations for gimp brushes, locally or globally - you are trying to copy to the global folder and you need to be a super-user for this. Use a terminal and sudo nautilus to run. (It has a red background for a reason - be careful) Unless absolutely necessary, better to use your local gimp brushes folder in your home directory. see: